A charge pump is provided in the HST hydraulic circuit so as to replenish the hydraulic circuit with oil. There are circuits known in the related art that cool HST hydraulic circuits by pressure oil (i.e., pressurized hydraulic oil) from charge pumps (refer to, for example, Patent Reference Literature #1). In the circuit disclosed in Patent Reference Literature #1, pressure oil from the charge pump that is relieved through a charge relief valve is guided to a reservoir through a pump case, a motor case, and an oil cooler.    Patent Reference Literature 1: Japanese Laid Open Patent Publication No. 2005-54964